1. Field of the Invention
The present invention relates generally to a system and apparatus for preventing and removing ice build-up on an aircraft, and more particularly to a heat exchanger which utilizes the heat energy from the exhaust gas in the turbine engine to deice exposed portions of an aircraft.
2. Previous Methods
Certain techniques for preventing and removing ice from exposed, air flow surface portions of an aircraft are known. One technique utilizes hot, compressed air from the discharge region of the engine compressor called "bleed air." A portion of the total engine bleed air available is routed to the various exposed aircraft portions which are subjected to icing, and then exhausted overboard. Such a technique is shown in Rumford, et al., U.S. Pat. No. 4,783,026; McLaren, et al., U.S. Pat. No. 5,011,098; Cole, et al., U.S. Pat. No. 4,674,714; Thomas, U.S. Pat. No. 2,514,105; Palmatier, U.S. Pat. No. 2,556,736; Cook, et al., U.S. Pat. No. 3,993,327; Pouit, U.S. Pat. No. 2,645,435; Krueger, U.S. Pat. No. 2,868,483; and Messinger, et al., U.S. Pat. No. 2,563,054.
Another known technique uses electrical resistive elements formed integrally with the exposed portions of the aircraft. The electrical resistive elements are electrically connected to onboard generators and heat the exposed portions of the aircraft.
Another technique utilizes bladders or other mechanical structure on the exposed portions of the aircraft. The bladders are driven by pneumatic pumps and are designed to mechanically deform to shed ice build-up. A still further technique utilizes chemicals stored on board which are applied as necessary to the exposed portions of the aircraft to remove and/or prevent ice build-up.
While these known techniques can be useful in preventing and/or removing ice on the exposed portions of the aircraft, these techniques are not without drawbacks.
For example, the compressor bleed air technique described above can impair the performance of the engine, and hence increase fuel consumption. Fuel consumption has become an important consideration in aircraft design. Electrical resistive techniques can require electrically complex systems. Additionally, the electrical and mechanical techniques can also tax the engines to drive the necessary equipment, such as generators or pneumatic pumps. Finally, the chemical techniques can increase the overall weight of the aircraft, thus also increasing fuel consumption.
It is known that heat transfer fluid has been used to transfer heat energy away from a location on an aircraft. For example, it is known to provide a pair of plates sealed together around the edges to form a plenum, and to dispose heat transfer fluid within the plenum. The inner of the two plates is then located in contact with an exterior wall portion of the aircraft, such as against the surface of the turbine engine, and heat energy is bled away from the engine to prevent over-heating of engine components and accessories (e.g., gear systems, drive generators, etc). It is believed this technique would not be useful in transferring heat energy to an exposed portion of an aircraft to de-ice the aircraft because: (i) this technique would require a large number of heat transfer devices to draw enough heat energy from the walls of the engine so as to be useful; and (ii) even if one of the plates was located within (in direct contact with) the exhaust gas stream of the engine, the plate would degrade rapidly because it is not formed from a material which could withstand prolonged contact with the exhaust gas, and the heat transfer fluid would have to be continuously moved between the plates so as to prevent boiling or vaporization of the fluid, thus always burdening the engines even when it is not necessary to de-ice the aircraft.
Hence, there is a demand in the industry for a simple and effective system for preventing and removing ice on exposed portions of aircraft, and in particular for a system which does not significantly burden or tax the aircraft engines and, therefore, does not negatively impact the specific fuel consumption of the engines.